How can I not let parties stress me out?

What are you stressing over? Are you trying to do everything TOO perfect?

Perhaps you could "co-host" a party so that some of the stress and workload are elsewhere. If serving a meal, assign guests to bring items... someone brings a salad, another a vegetable, another dessert, etc so that you don't have all the prep. If you are concerned about the appearance of your house, consider hiring a cleaning service a day or two before the event. Allow them to do the heavy cleaning so you can concentrate on other arrangements.

yeah what are you stressing about? i know in the beginning i like to make sure everything is good, food, drinks, everyone is having a nice time then when everything is fine, i start enjoying myself.

Well I would say first RELAX. If you go into thinking (oh gosh, I gotta hear her mouth or I hope so and so doesnt' come or I just want to get this over with) like i have done many times before.. The day is completely lost. If you have those negative nellies that will be there just know they will be like they always are and let it go. Or like me with my mom who never has a positive thing come out her mouth. Just let it go in and out. I know it can be hard to do but when I let the neg. thoughts go and tell myself positive ones as hard as it is it does help!

Plan so that you can do things ahead of time. Designate people to bring foods for potluck. Depending on how many peoplke are invited, have one person bring salad, one bring desert, one or two bring veggies, one bring bread, and bring your own drinks. Have a friend help with clean-up before and after. If you must have decorations, plan to do it several days in advance, if possible, or stretch it out over a couple of days. I have the big plastic totes with holiday decor. Each is marked. When I use one, put it back on bottom so that the next one on top is for the next holiday. No digging for what you want.